When you move the mouse cursor over a table, you will see all primary key fields, but they are not always in that order of Field Nos. E.g. "Stockkeeping Unit" table

Move over details of table in AL, fields are sorted by Field No.:
(local) SKU: Record "Stockkeeping Unit"
"Item No." * Code[20]
"Variant Code" * Code[10]
"Location Code" * Code[10]
Description Text[100]
[..]

But the primary key of "Stockkeeping Unit is "Location Code", "Item No.", "Variant Code" and a SKU.Get("Item No.", "Variant Code", "Location Code") does not work.